As a kind of display devices, there is a commercially utilized structure including a liquid crystal display panel and a backlight with light sources disposed immediately below thereof. There is a proposed technique that, when adjacent light sources in a backlight are all turned on, the total strength of the light is made substantially even. Furthermore, there is another proposed technique that, when an image displayed in a head-up display, a range of the displayed image is recognized to turn on light sources corresponding to the range in order to reduce the power and to suppress heating. Furthermore, there is another proposed technique that a direct backlight has step pyramid holes in a holder tapered from the light emitting element side to the light emitting surface in order to reduce unevenness in the brightness. The direct backlight is also called straight fall type backlight.
When a light source array in which light sources are arranged at certain intervals is driven, it is required to reduce unevenness in the brightness caused by a dim line with low brightness and a bright line with high brightness. Furthermore, a display device including such an illumination device is required to suppress deterioration of display quality caused by such unevenness in the brightness of the illumination device.